Vibrating mill with introduction of refrigerants into the solid material being ground in the grinding chamber

ABSTRACT

A vibrating mill for grinding solid materials is provided with a grinding chamber with at least one or a plurality of spaced feed pipes for refrigerants which terminate within the body of the solid material being ground within the grinding chamber and the amount of the refrigerants introduced is controlled by temperature probe or probes which control valves in said feed pipes.

United States Patent 1191 Langmaack et al.

VIBRATING MILL WITH INTRODUCTION OF REFRIGERANTS INTO THE SOLID MATERIAL BEING GROUND IN THE GRINDING CHAMBER Inventors: Jiirgen Langrnaa clt, Niederkassel;

Helmut Haas, Cologne, both of Germany xlfl9 n 'filmb ld rpfllil Aktiengesellschaft, Cologne, Germany Filed: Nov. 18, 1971 Appl. No.: 199,933

Assignee:

Foreign Application Priority Data Nov. 21, 1970 Germany P 20 57 428.1

- 241/153,241/175 1111. C1. B02c 17/14 Field of Search 241/33, 38, 41, 42,

[ Jan. 15, 1974 [56] References Cited UNITED STATES PATENTS 3,633,830 l/1972 Oberpriller 241/18 3,272,443 9/1966 Reiners et a1... 241/153 2,561,043 7/1951 Ayers 241/32 X 3,295,791 1/1967 Maeder 241/153 3,658,259 4/1972 Ledergerber 241/65 X Primary Examiner-Granville Custer, Jr. Att0rney-Benjamin H. Sherman et a1.

[57] ABSTRACT A vibrating mill for grinding solid materials is provided with a grinding chamber with at least one or a plurality of spaced feed pipes for refrigerants which terminate within the body of the solid material being ground within the grinding chamber and the amount of the refrigerants introduced is controlled by temperature probe or probes which control valves in said feed pipes.

9 Claims, Drawing Figure 1 VIBRATING MILL wITII INTRODUCTION OF REFRIGERANTS INTo THE SOLID MATERIAL BEING GROUND IN THE GRINDING CHAMBER The invention relates to a vibrating mill for the comminution of solid materials with addition of refrigerants into the grinding chamber.

The German Laid Out Specification No. 1,004,460 discloses a device for cold grinding of solid, viscous materials, in which the materials to be groundfor example thermoplastic synthetic materials-before the introduction into the grinding device, are conveyed through a cooling device filled with liquid nitrogen, in which the synthetic materials to be comminuted are embrittled. For the cooling of the supply conduits and of the grinding chamber itself, the vapors produced by the liquid bath of the cooling device are conveyed through the grinding device.

lt was now found that this known method for the cooling of the grinding device was not sufficient, particularly upon fine comminution in a vibrating mill where quantities of heat are released which must be discharged in another manner than is described in the known device.

In accordance with the invention in the disadvantages of the known device are overcome that on the vibrating mill one or-viewed in longitudinal direction of the grinding chamber-several feed apertures for refrigerant provided with valves are arranged consecutively and discharge below the surface of the material to be ground in the grinding chamber. This method compared with the known method in which the vapors obviously can be introduced solely into the chamber above the surface of the material, has the advantage that the additionally introduced refrigerant is also in the grinding chamber itself and is immediately brought into direct contact with the material being ground, so that it is also available directly where the quantities of heat produced by the grinding operation are released. This is particularly of importance for substances which-like a number of synthetic materialshave a low heat conductibility and above all for substances in which the temperature of the embrittling point lies only slightly above the temperature of the refrigerant introduced into the grinding chamber. In such cases, the rapid removal of the quantities of heat produced by the grinding operation and emanating, from the material being ground is of appreciable importance, whereby through the direct contact of the refrigerant introduced directly into the material being ground, the necessary quantities of refrigerant as compared with the known method may be held low, which both in respect to the economy of the grinding operation as well as the degree of efficiency of the grinding method with respect to the small quantities of gas to be removed is advantageous.

Another object of the invention is that thefeed openings for the refrigerant are arranged on the side of the grinding chamber, on which under the influence of the vibrating movement, a movement of the material being ground in a downward direction takes place. Hereby, in an advantageous manner, the movement of the material being ground in the grinding chamber is made use of for the transportation and for the distribution of the refrigerant introduced into the lower areas of the material being ground. A further advantage of this arrangement is that the formation of the feed apertures for the refrigerant, which must be protected with respect to a 2 direct contact with the grinding bodies, is relatively simple.

Still another object of the invention is that one or several valves of the feed openings are controllably connected in each case with a temperature probe whichin axial direction of the grinding chamber and viewed from the material feed point-is arranged spaced behind at least one feed'opening and is in connection with the interior of the grinding chamber. Through this arrangement a rise in the temperature can be determined in longitudinal direction of the grinding container in the direction of passage of the material in a simple manner, and accordingly one may introduce as much refrigerant through one or more of the feed openings lying in front so that a predetermined minimum temperature of the material is not exceeded.

In an advantageous development of the invention, it is furthermore provided that at least one temperature probe is so arranged on the grinding container so that it is in contact with the grinding material. Thereby when the temperature probe is in contact with the grinding material it avoids merely taking the temperature of the gas flow above the surface of the material in the free space of the grinding container.

As in this arrangement of the temperature probe the material temperature is detected more accurately, it is to be expected that temperature changes will be recognized more rapidly, and thus upon the connection of the valves with the temperature probes to automatic control circuits, the idle time periods are few. The consumption of refrigerants therefore may be reduced.

The'number of the feed apertures for the refrigerant distributed over the length of the grinding container depends essentially on the length of the grinding container, and the passage time of the material to be ground. With a very fine comminution, the passage time for the material through the grinding container may amount to one hour and more, so that refrigerant must be introduced at several locations of the grinding container. Probes and the problem of how many feed valves are to be connected with one temperature probe in case of an automatic regulation depends likewise on the characteristics of the individual case. According to the length of the grinding container and the characteristics of the material to be ground, the injection of the quantities of refrigerant through all the feed openings lying in front-viewed in direction of passage of the material-may be regulated through only one temperature probe which is advantageously arranged in the area of the material discharge opening of the grinding container.

In a preferred embodiment, a vibrating mill in which the grinding container is provided directly in front of the material discharge aperture with a separating wall, which holds back the grinding bodies but permits the passage of the comminuted material, the temperature probe projects into the area behind the separating wall into the comminuted material. This makes it possible to introduce the temperature probe deeply into the flow of material being ground, without special protective measures having to be provided with respect of the grinding bodies.

The drawing diagrammatically illustrates an example of a grinding arrangement of the invention and which explains the grinding of solid substances at low temperatures in a vibrating mill, in accordance with the invention.

A vibrating mill with two horizontal parallel and vertically spaced grinding tubes 1 and 2, which are supported in a carrier frame 3 provided with a vibrating drive, has one end of its upper grinding tube 1 connected by a material-inlet opening 4 with a cooling device not illustrated for the material to be ground. The two grinding tubes 1 and 2 are connected together at the end of the grinding tube 1 facing away from the material inlet opening 4 by a vertical connecting pipe 5. The grinding tube 2 has at its end facing away from the inlet of the connecting pipe 5 a material discharge 6, which discharges into a collecting container 7 for the material which has been ground.

The embrittled material to be ground passes from the cooling device through the material inlet opening 4 into the grinding tube 1. Under the influence of the vibrating movements and of the constantly flowing material, the individual particles of material travel in the direction of the arrow 8 through the grinding tube filled with grinding bodies. Through a separating wall 9 provided with fine holes, which insure the passage of the comminuted material, but hold back the grinding bodies in the grinding tube 1, the comminuted material passes through the connecting pipe 5 into the grinding tube 2 which likewise is filled with grinding bodies. Also here the material travels under the influence of the vibrating movements and the material flowing thereafter from the inlet aperture of the connecting pipe 5 in the direction of the arrow 9a to the discharge 6 of the grinding tube 2 into the collection container 7.

In order to compensate for the heat resulting in the course of the grinding operation and the cold losses occurring in spite of the arrangement of insulating sleeves on the grinding tubes, a feed pipe 11 extends into the material to be ground in the grinding tube 1. This feed pipe which'for reasons of the better distribution of refrigerant and for the lowering of the inlet speed may advantageously have several parallel or divergingly constructed nozzle openings, is suitably arranged to extend through the end face of the grinding tube. For the regulation of the quantity of refrigerant to be introduced into the grinding tube, a control valve 12 is arranged in the refrigerant inlet of the feed pipe 11. This control valve, in the event of the equipment of the grinding installation is provided with an automatic regulation of the feed of the refrigerant into the grinding chamber, may be provided with a motor-driven, pneumatic or electromagnetically actuated adjusting device.

Viewed in the direction of the arrow 8 there is arranged spaced behind the inlet of the feed pipe 11 a temperature probe 13. Through' this temperature probe, which suitably is arranged on the grinding container so that it is in direct contact with the material to be ground, the quantity of refrigerant to be injected by the feed pipe 11 is regulated in dependence on the material temperature. In case of an automatic regulation, the value measured by the temperature pipefor example a thermo-elementis supplied as theoretical value ofa regulating device 14 which adjusts the adjusting device of the control valve 12 corresponding to the predetermined theoretical values.

With longer tubular grinding containers and/or longer duration of the material to be ground in the grinding container it is suitable to introduce refrigerant at least at one further point into the material to be ground in order to make the rise in temperature retrogressive, which is brought about through the heat becoming released by the grinding operation. Hereto is arranged, for example, approximately in the center of the grinding container-referred to the longitudinal directiona further feed opening or pipe 15 for refrigerant, which discharges below the surface of the material to be ground. Advantageously, the feed pipe 15 is arranged on the side of the grinding container on which under effect of the vibrating movement, the grinding material carries out a movement directed downwardly according to the arrow 16. The feed pipe which may have several parallel or divergently directed nozzle openings, must be covered on the inner side of the grinding container for protection against disturbances through the grinding bodies. Also this feed pipe is connected with a control valve 17 to the refrigerant supplier.

For the determination of the material temperature, a temperature probe 18 is advantageously arranged in the area of the discharge opening of the grinding container 1, and in the rear of the perforated disc 9. In this space formed between the perforated disc 9 and the end wall 19 of the grinding container 1, there may for example be disposed through an overflow device 20 the inlet opening for the connecting pipe 5 in such a manner that the material passing through the perforated disc 9 first is dammed up or retained in this chamber, so that the temperature probe 18 may be inserted deeply into the ground material and thus quite an accurate value of the grinding material temperature may be determined.

In the case of an automatic regulation, the temperature probe 18 is also provided with a regulating device 21 which operates the control valve 17. Since the arrangement of the temperature probe 18 at the discharge end of the grinding container 1 insures quite an accurate determination of the material temperatureacco,rding to the characteristics of the substance to be comminuted, the quality of the insulation, the length of. the grinding container, etc.it may be sufficient if the feed of refrigerant is regulated solely by this temperature probe 18, so that the other temperature probe 13 with the corresponding regulating device 14 may not be necessary. In such a case the regulating device 21 and also the control valve 12 are connected with the feed pipe 11, as shown by the dash-dotted line 22.

Since the illustrated embodiment shows by way of example a vibrating mill which operates continuously and in which continuously the material to be ground passes through and correspondinly simultaneously grinding heat is released, the regulating device 21 may to advantage be so constructed that through the feed pipe 11 continuously or at uniform periods of time through the feed pipe 11 and if need be through the feed opening 15, a quantity of refrigerant regarded as constant in timing is supplied. Upon exceeding the minimum temperature of the material in the discharge housing, measured by the temperature probe 18, then up to a predetermined quantity of refrigerant limited by the regulator, a larger quantity of refrigerant may be introduced through the feed pipe 15. If the rise of temperature in the ground material requires a still greater quantity of refrigerant, then the inference may be that already at the injecting point 15, the minimum material temperature is exceeded, so that additionally the quantities of perature probe 13 shown in the drawing as auxiliary regulating size of the regulating device 21. In this manher, the inoperative periods" and an oscillation of the regulating circuit may be appreciably diminished.

The construction of the vibrating mill in accordance with the invention is not limited to the arrangement of only two supply openings for refrigerant and correspondingly one or two temperature probes, but according to the requirements of the particular case, there may be arranged in longitudinal direction of the grinding container also several feed openings for refrigerant consecutively. whose regulating valves individually or combined into groups are connected with the regulating device. As shown in the drawing, the grinding container 2 is provided in a manner similar to the grinding container 1 with feed pipes or openings for refrigerant and corresponding temperatures probes and regulating devices.

Since now upon introduction of liquid refrigerants, for example liquid nitrogen, the latter evaporate under the influence of the grinding heat, it is suitable and of advantage when at each grinding container, at least one discharge opening 23, 24 is arranged for the gasified refrigerant. According to the quantities of the injected refrigerant, it is advantageous when several feed openings for refrigerant are employed to arrange in each case in the area in front of a further feed opening, a discharge opening, so that the flow of gas above the surface of the material in the grinding container may be held low. Suitably, the discharge of the gases is controlled by control valves, which advantageously are regulated in dependence upon the pressure in the grinding chamber. In such cases the vibrating mill is closed off with material charging valves impervious to gas, for example bucket-wheel charging valves 25 with respect to the aggregates connected at the inlet or outlet side. The arrangement of such a charging valve is indicated in the feed pipe 26.

What we claim is:

1. A vibrating mill for the grinding of solid substances comprising in combination:

a horizontal elongate grinding chamber;

a material feed inlet at one end of the chamber;

a material feed outlet at the other end of the chamber;

a vibratory drive means connected to the chamber for grinding material therein;

an inlet for refrigerant leading into the chamber for the discharge of refrigerant into the material being ground;

and a control valve means for said inlet controlling refrigerant flow into the chamber through said inlet.

2. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

wherein a refrigerant outlet is located between said material inlet and outlets and spaced from the top of the chamber to be submerged beneath the level of the material being ground in the chamber. 3. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

including a valve connected to said refrigerant inlet for controlling the flow of refrigerant into the chamber; and a temperature sensitive probe within the chamber operatively connected to control the valve responsive to the temperature of material being ground therein. 4. A vibrating mill for the grinding of solid substances constructed in accordance with claim 3:

wherein said probe is located adjacent said material Outlet. 5. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

and including a refrigerant gas outlet adjacent the top of the chamber for the escape of refrigerant entering the chamber through said opening. 6. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

including a material separating screen across the outlet end of said chamber so that material flowing through said outlet must pass said screen. 7. A vibrating mill for the grinding of solid substances constructed in accordance with claim 3:

wherein said probe is located upstream of said refrigerant outlet. 8. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

including a second chamber connected to said drive means and having an inlet connected to the material outlet for the first chamber and having an outlet at the end of the chamber opposite the material inlet; and means for directing a flow of refrigerant into said second chamber. 9. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1:

including a second refrigerant inlet leading into the chamber having an opening positioned near a lower portion of the chamber for discharging refrigerant below the material being processed; a screen across the discharge end of the chamber; first and second temperature sensitive probes for controlling inlet valves for respectively the first and second refrigerant inlets; a second chamber having an inlet connected to the outlet for the first chamber; an outlet for said second chamber at the end opposite the inlet end; a screen across the outlet end of said second chamber; a screen across the outlet end of said first chamber; first and second refrigerant inlets leading into said second chamber; and first and second temperature sensitive probes connected to valves for the refrigerant inlets for the second chamber and being positioned within the second chamber. 

1. A vibrating mill for the grinding of solid substances comprising in combination: a horizontal elongate grinding chamber; a material feed inlet at one end of the chamber; a material feed outlet at the other end of the chamber; a vibratory drive means connected to the chamber for grinding material therein; an inlet for refrigerant leading into the chamber for the discharge of refrigerant into the material being ground; and a control valve means for said inlet controlling refrigerant flow into the chamber through said inlet.
 2. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: wherein a refrigerant outlet is located between said material inlet and outlets and spaced from the top of the chamber to be submerged beneath the level of the material being ground in the chamber.
 3. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: including a valve connected to said refrigerant inlet for controlling the flow of refrigerant into the chamber; and a temperature sensitive probe within the chamber operatively connected to control the valve responsive to the temperature of material being ground therein.
 4. A vibrating mill for the grinding of solid substances constructed in accordance with claim 3: wherein said probe is located adjacent said material outlet.
 5. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: and including a refrigerant gas outlet adjacent the top of the chamber for the escape of refrigerant entering the chamber through said opening.
 6. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: including a material separating screen across the outlet end of said chamber so that material flowing through said outlet must pass said screen.
 7. A vibrating mill for the grinding of solid substances constructed in accordance with claim 3: wherein said probe is located upstream of said refrigerant outlet.
 8. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: including a second chamber connected to said drive means and having an inlet connected to the material outlet for the first chamber and having an outlet at the end of the chamber opposite the material inlet; and means for directing a flow of refrigerant into said second chamber.
 9. A vibrating mill for the grinding of solid substances constructed in accordance with claim 1: including a second refrigerant inlet leading into the chamber having an opening positioned near a lower portion of the chamber for discharging refrigerant below the material being processed; a screen across the discharge end of the chamber; first and second temperature sensitive probes for controlling inlet valves for respectively the first and second reFrigerant inlets; a second chamber having an inlet connected to the outlet for the first chamber; an outlet for said second chamber at the end opposite the inlet end; a screen across the outlet end of said second chamber; a screen across the outlet end of said first chamber; first and second refrigerant inlets leading into said second chamber; and first and second temperature sensitive probes connected to valves for the refrigerant inlets for the second chamber and being positioned within the second chamber. 